For example, the document “1.25-Gb/s Regulated Cascode CMOS Transimpedance Amplifier for Gigabit Ethernet (registered trade name) Applications”, IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 39, NO. 1, JANUARY 2004 (Non-Patent Document 1) describes a transimpedance amplifier which converts a current signal from a photo diode to a voltage signal and amplifies the signal in a high speed optical receiver. Particularly, a regulated cascode amplifier circuit is optimal as a transimpedance amplifier for which high-speed operation of several Gbps or higher is required.